A severe problem of TEA lasers is the arcing that can occur during the main discharge between the electrodes. Many schemes have been developed to prevent arcing. They normally avoid concentration of electric field by providing for appropriately shaped main electrodes. They also provide for preionization of laser gas mixture so that a more uniform main discharge can take place throughout the length of the electrodes. One or more wires can be positioned longitudinally and adjacent to the main discharge region such that a subsidiary discharge between the wire and one of the electrodes serves as the preionizing mechanism. A drawback of this scheme is that the wire is a fragile component and can break due to mechanical shock. A multi-electrodes flash-board can be provided such that a subsidiary discharge can take place between the electrodes of the flash-board. A problem that arises in flash board systems is that there is a contamination of the laser tube by chemical compounds created by the reaction of some of the ions of the flash-board electrode material and the ionized gas of laser. The structure of some preionizing electrodes is that of a very thin disk, such as that obtained by a flame spraying technique. A disadvantage that arises is that the energy of the discharge might damage the very thin edges of these electrodes, since they do not have much mass and cannot dissipate the energy effectively. Additionally, the discharge takes place along the surface of the supporting structure further contributing to contamination.